In JP-P2000-356561A, a pressure sensor, includes a semiconductor a sensor element adhered to a lead frame and mounted in a resin package member via the lead frame. Further, the pressure sensor is provided with a non-contact space between the package member and an area where the sensor element is mounted in the lead frame. The sensor is thereby restricted from thermal hysteresis. Here, thermal hysteresis is a phenomenon in which sensor characteristic changes from an initial characteristic due to a cooling-heating cycle with repeat of high and low temperatures. However, in view of cost reduction, it has been recently desired that the sensor element is directly adhered to the package member with an adhesive without the lead frame.
When the sensor element is mounted in the package member via the lead frame, surfaces of a lead portion and land portion in the lead frame are located on the same plane. Therefore, a level gap (step portion) is formed between surfaces of the lead portion and the sensor element mounted on the island portion, and is necessary to bond the land portion and the sensor element with a wire. Here, to upgrade wire-bonding performance, the surfaces of the sensor element and the lead portion are preferably on the same plane.
Removal of the island portion under the sensor therefore leads to flexible designing of the component layout to possibly set the two bonded surfaces on the same plane. It has been hence desired that the sensor is adhered on the package member with an adhesive layer without using the lead frame.
However, when the above direct adhesion of the sensor element to the package member is performed, the thermal hysteresis is readily generated by a difference of thermal expansion coefficients among the sensor, the adhesive and the package member.